1. Field of the Invention
The invention relates to a vehicle headlamp configured to form a predetermined light distribution pattern. More particularly, the invention relates to a vehicle headlamp using a plurality of lamp units having light-emitting diodes as light sources including a projector-type lamp unit, a direct-projection-type lamp unit, and a reflection-type lamp unit.
2. Description of the Related Art
A light-emitting diode has been used as a light source of a vehicle marker lamp such as a tail lamp. For instance, JP-A-2002-50214 describes a vehicle marker lamp in which a plurality of lamp units, each unit using a light-emitting diode as a light source, are arranged.
JP-A-2001-266620 describes a vehicle headlamp. The headlamp is constructed such that a desired light distribution pattern is formed by selectively illuminating a portion of a plurality of light-emitting diodes arranged in a matrix layout.
The lamp configuration described in JP-A-2001-266620 enables changing of the shape of a light distribution pattern by division into an illuminating region and a non-illuminating region, but encounters difficulty in forming a light distribution pattern with a desired distribution of luminous intensity.
Another conceivable lamp configuration can be applied to the vehicle headlamp, such as that described in JP-A-2002-50214, wherein a plurality of lamp units, each unit employing a light-emitting diode as a light source, are arranged. However, in such a case the following problem will arise.
Mere use of a plurality of identical lamp units in the manner as described in JP-A-2002-50214 results in light distribution patterns formed through radiation of light from the respective lamp units becoming identical with each other in terms of a pattern geometry and the distribution of luminous intensity. Therefore, there arises a problem of a failure to form a light distribution pattern of a vehicle headlamp obtained as a merged light distribution pattern in the form of a desired pattern geometry and a desired distribution of luminous intensity.
The invention has been conceived in view of the aforementioned circumstances and aims at providing a vehicle headlamp which is constructed to form a predetermined light distribution pattern and enables formation of a light distribution pattern in a desired pattern geometry and a desired distribution of luminous intensity even when a semiconductor light-emitting element is used as a light source of the headlamp.